Does he still has forwarder channels on his system menu? If yes, he can use that as an exploit to reinstall the homebrew channel instead of what modmii suggests. If he still has the homebrew channel*, then can even skip the exploit and get to reinstalling the cIOS'es that were stubbed in the process.

If he has no custom channel whatsoever...then he'll need one of the games that has an exploit.

*the latest version of that channel doesn't get removed in the update process